1. Field of the Invention
The present invention relates generally to an implantation device and, more particularly, but not way of limitation, to an implantation device designed for loading with a surgical implant and for subsequent delivery of the surgical implant. The implantation device uses jaws and a slider to secure a surgical implant and allow implantation into a patient.
2. Description of the Related Art
Shape memory implants are commonly used in surgical procedures that require the reattachment or fusing of tissue or bone. Shape memory implants can be composed of shape memory material such as Nitinol that allows the shape memory implants to have a first final shape and the ability to transform into a second shape. A shape memory implant can be either thermally activated, in which an external heating source or body temperature would be required to activate the implant, or mechanically activated, in which a constraining instrument would be required. A shape memory implant that requires mechanical constraint stores mechanical energy due to elastic (recoverable) deformation, and then releases the stored mechanical energy when the constraint is removed. In these types of implants, the implants are mechanically deformed into their second shape and maintained in their second shape by instrumentation such that, upon release from the instrumentation, the implants elastically deform from their second shape into their first final shape.
In surgical procedures, the elastic property of constrained shape memory implants is used as follows. Bones that require fixating are aligned, and the shape memory implant, which has been mechanically deformed to its second shape, is maintained in instrumentation and inserted between the bones. In the second shape, the legs of the implant are generally parallel. After insertion, the shape memory implant is released from the instrumentation, whereupon the shape memory implant elastically returns to its first final shape such that the shape memory implant maintains the bones fixated together. In the first final shape, the legs of the implant are converging at the tips. Because the shape memory implant stores mechanical energy, it continuously applies force to the fixated bones as the shape memory implant transitions from the second shape to the first final shape, which aids in the healing process.
Various types of instrumentation can be used for either maintaining the shape memory implants in their second shape or moving an implant from its first final shape to a temporary second shape. Some companies used metal forceps to open and insert the shape memory implant. These forceps have to be sterilized by a hospital, and then a shape memory implant can be placed on the forceps, opened to a desired position, and used for inserting the implant. Although potentially effective, forceps require the implant to be loaded into the forceps during surgery, which might be cumbersome and time consuming. In addition, forceps might be large which could hinder implantation of the shape memory implant into a patient during surgery. It is also possible that a physician using the forceps might damage the shape memory implant in various ways, such as stretching the implant beyond the second shape, fatiguing the implant, or causing metal-on-metal scraping of the implant with the instrument. Furthermore, forceps can be expensive instruments that require cleaning and sterilization after each surgery.
Other companies use plastic and disposable tools to maintain a shape memory implant in the second shape. This type of instrumentation can be preloaded and sterilized with the implant already in the second shape, and the implant can be pre-activated so that it does not require heating with an external heater or body temperature after use. One type of plastic and disposable instrument operates by having the implant fit inside a passage that is substantially the same diameter as the shape memory implant. By using this method, the implant insertion device allows the shape memory implant to be preloaded prior to surgery. However, using an implant insertion device that substantially conforms to the profile of the shape memory implant can create several problems for a surgeon. First, this type of implant insertion device often makes disengagement of the shape memory staple after implantation problematic. In particular, the shape memory implant sticks to the implant insertion device due to the frictional engagement between the shape memory implant, which is trying to compress, and the passage of the implant insertion device, resulting in a more difficult surgical procedure and the potential for a less than satisfactory fixation of tissue or bone. Second, this type of implant insertion device results in an abrupt and sudden release of stored mechanical energy as the implant is removed from the device. This type of implant insertion device provides no method by which to slowly transition the stored energy in the implant from the implant insertion device to the bones that are being fixated. Finally, this type of implant insertion device can result in entanglement during release, in which the implant legs begin to compress upon release and make extraction of this type of insertion device more difficult.
Accordingly, an instrument that constrains a shape memory implant in its second shape, allows the shape memory implant to be preloaded and sterilized prior to surgery, simplifies removal of the shape memory implant after partial implantation, and controls the rate of release of tension would be beneficial.